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Green deposit on copper pipe at fittings

Some copper water pipe solder fittings have a residue of green gunge
around them, due to the finished solder joints not being effectively
cleaned after soldering.after new CH installation around 5 years ago.

First Q: What is the green gunge (chemically)? Does the deposit have
common or garden name? It must be a Cu compound, but how is it formed
from solder flux, copper, solder & propane gas used in the torch?

Second Q: What is the most effective method of cleaning it off,
especialy when it has been on the Cu pipes several years? I'd like to
get the area around the fittings reasonably chemically clean. I fancy
just cleaning with wire wool might leave a residue for the green to
re-crystallize on.

Third Q: I thought I had cleaned the joints at the time, so how should
soldered work be cleaned to avoid green film formation?

marbles wrote:
Some copper water pipe solder fittings have a residue of green gunge
around them, due to the finished solder joints not being effectively
cleaned after soldering.after new CH installation around 5 years ago.

Resues of acid/active flux, I believe. The active flux contains
hydrochloric acid which removes the surface oxide layer &
'cleans'/pickles the pipe and fitting when heated, prior to the solder
melting & running.

I don't know what the green compound is, I'm sure a chemist will be
along shortly. If left inside a heating system, the acidic flux
residues can cause serious problems with corrosion.

In article . com,
marbles wrote:
Some copper water pipe solder fittings have a residue of green gunge
around them, due to the finished solder joints not being effectively
cleaned after soldering.after new CH installation around 5 years ago.
First Q: What is the green gunge (chemically)? Does the deposit have
common or garden name? It must be a Cu compound, but how is it formed
from solder flux, copper, solder & propane gas used in the torch?

It comes from the use of acid flux, and not cleaning any excess off
afterwards. Shouldn't do any harm, though.
Second Q: What is the most effective method of cleaning it off,
especialy when it has been on the Cu pipes several years? I'd like to
get the area around the fittings reasonably chemically clean. I fancy
just cleaning with wire wool might leave a residue for the green to
re-crystallize on.

Water and wire wool or any other suitable abrasive. Car paint wet or dry
paper if you have any lying around. Wash off with clean water afterwards.
Third Q: I thought I had cleaned the joints at the time, so how should
soldered work be cleaned to avoid green film formation?

You normally wipe the joint with a wet rag once the solder has set.

--
*I didn't fight my way to the top of the food chain to be a vegetarian.

Dave Plowman (News) wrote:
Doesn't it get diluted by the water to the extent it can't do anything? It
also seems to stop corroding the outside after a while - the reaction
becomes used up.

Unless flushed out &/or neutralised, I believe it makes the water
acidic (pH7) and this then starts off galvanic corrosion with the
steel radiators anode and copper pipes cathode.
If inhibitors are added, you usually wind up with water pH of 8 or 9.

An old fitter commented that they didn't used to have acid flux and he
didn't often see the corrosion problems you get with central heating
these days..

marbles wrote:
Some copper water pipe solder fittings have a residue of green gunge
around them, due to the finished solder joints not being effectively
cleaned after soldering.after new CH installation around 5 years ago.

First Q: What is the green gunge (chemically)? Does the deposit have
common or garden name? It must be a Cu compound, but how is it formed
from solder flux, copper, solder & propane gas used in the torch?

I'd say ots PROBABLY copper carbonate...sort of natural end point of any
copper type oxide and CO2..
Second Q: What is the most effective method of cleaning it off,
especialy when it has been on the Cu pipes several years? I'd like to
get the area around the fittings reasonably chemically clean. I fancy
just cleaning with wire wool might leave a residue for the green to
re-crystallize on.

Ni. The reaon its around the joints is they they have a flux residue
usually. And have been heated. If you WASH the joint and then wool it
up, it stays good, usually

Third Q: I thought I had cleaned the joints at the time, so how should
soldered work be cleaned to avoid green film formation?